Tuesday, April 4, 2017

The Loose Connection Between Disease Definition, Addiction, and Neuroscience

Carl Hart is a neuroscience professor and department head at Columbia. He wrote an opinion piece in the first edition of the new journal Nature Human Behavior about the social consequences of calling addiction a brain disease. The original article is reference 1 below with a link. I encourage anyone interested to read it several times. I say that because the concepts contained in the article are emotional, confusing, and politicized. Repeated reading allows a clearer picture of these concepts.

In the introduction he discusses his early hope that by learning neuroscience and curing addiction "through neural manipulations" that he could help rid resource poor communities of crime and poverty. His main arguments against the notion that addiction is a "disease" is that the majority of people who use a drug do not become addicted and the old argument that is typically used against psychiatric disorders - there is no actual lesion in the brain to differentiate the addicted from the non-addicted. He uses the example of Huntington's or Parkinson's Disease as brain diseases that nobody would argue with.

The form of those initial premises should not be lost on any student of rhetoric because one does not follow the other. With any disease that occurs as a result of environmental exposure, it is likely that a large percentage of the exposed population will not develop the disease. A lot of that depends on the toxicity of the exposure and the personal biology of the exposed. One of the best examples is alcohol exposure. It takes a certain amount of exposure to cause pancreatitis and cirrhosis both of which cause observable end organ damage and yet the vast majority of people exposed to alcohol develop neither. The epidemiological estimates are also group averaged effects, so it is possible to observe outliers who ingested well beyond the suggested dose necessary to produce the disease and yet they have no evidence of damage.

The results are even more variable when it comes to Wernicke-Korsakoff syndrome an alcohol related illness caused by thiamine deficiency. The vast majority of alcoholics never develop the symptoms but a significant number of people do and there are a significant number who are diagnosed at autopsy but not when they are alive (5). An autopsy diagnosis is possible because of discrete brain lesions caused by the disorder.

The brain lesion argument is inaccurate at a number of levels. First, equating disease with brain lesion is not accurate. Medical diagnostic terminology has always been approximate rather than precise when it comes to pathognomonic lesions. There are very few. Nobody seems to argue that migraine headaches or cluster headaches are not diseases with significant disability. Despite the fact that there are no brain lesions like neurodegenerative diseases or "identified biological substrates" that differentiate migraine patients from the rest of the population. Syndenham pointed out that there are disorders are identified based on a consistent pattern of symptoms, family history, a natural history and course and predictable response to treatment. This general trend led Merskey to say:

There is no royal road to medical diagnosis. For every condition with a defined lesion there will be several with no lesion at all. My favorite is cervicalgia or neck pain. If you follow ICD 10 codes it is M54.2. It is no small problem because at least half of the population aged 65 or older had significant degenerative arthritis and much of this is in the spine. To make things even more nonspecific, practically all of these patients will have abnormal imaging studies of the spine. Unless there is a clear finding on physical exam or by electrophysiological testing the pain cannot be attributed to any specific lesion. As the pain becomes chronic there is even less connection to any underlying anatomy or physiology. Connections between "real" diseases and biological substrates are not hard and fast by any means.

In addition to Syndenham's approach to disease definition, there is a common sense approach. Even when psychiatric disorders and addictions have no clear laboratory test, polls indicate that they are generally recognized as diseases by physicians and the public in general. I would argue that all physicians encounter the severest problems in both groups of people. I speculate that the public realizes that uncontrolled use of an intoxicant to the point that it disrupts your life and leads to steady psychosocial deterioration to the point that all of your significant relationships are lost and you are unable to self correct - is a form of disease very close to severe psychiatric problems. Severe life-threatening problems that are beyond a person's capacity to self correct are seen as diseases.

Dr. Hart's next argument is one that has been found in the media over the past two years - more research funding should be directed at the psychosocial aspects of addiction rather than the neurobiological and basic science aspects. We have seen this line of reasoning applied to a Stanley Foundation grant to look at the genetics of psychiatric disorders and the National Institute or Health budget itself. It is generally a utilitarian argument based on the premise that basic science and brain research produces no useful solutions or that there has been a lack of focus on psychosocial determinants or consequences of drug use or addiction. If the initial argument is that most people who use drugs do not get addicted - it does not follow that there would be widespread consequences. In terms of determinants, they have been studied in many cases in detail and in the context of racial disparities in care (2-4). But studying them and even applying common sense does not produce a solution. The clearest example is 40 years of research on psychotherapies that are effective and designing a health system designed to ignore that fact. With addiction the psychosocial research has even more readily been ignored.

The argument about how the diseased brain model leads to unrealistic policies is quite a stretch. Dr. Hart suggests that such a model only allows for two solutions - focus on the diseased brain or focus on removing the drug from society. He incorrectly concludes that any focus on the brain removes an interest in socioeconomic factors in "maintaining or mediating drug addiction." Practically any available treatment for addiction whether it involves residential or outpatient treatment - cognitive behavioral therapy or twelve step recovery involves a comprehensive look at the psychosocial factors that may impede recovery or keep the cycle of addiction going. Do we really need further research to know that psychosocial factors increase the exposure to addictive drugs? After all the exposure is the first part of the problem. He has already concluded that the vast number of this exposed do not end up addicted. What is it about that exposure and that particular person who does end up with the addiction? How are they different and in any group will psychosocial determinants tell us why these differences exist?

He makes the statement: "The insidious assumption of the diseased brain theory is that any use of a certain drug is considered pathological, even the non-problematic, recreational use that characterizes the experience of the overwhelming majority who ingest these drugs." That statement is totally incorrect. People like me are treating people with addictions. By definition they have uncontrolled use of the drug to the point that they are no longer able to function. In many cases they have accumulated considerable medical and psychiatric comorbidity because of their inability to stop using drugs. That is what I am talking about when I consider addiction a brain based disease. It is a disease that involves the ingestion of an intoxicant with predictable long term consequences. That is not "recreational use." The issue of recreational use cannot be taken lightly. According to the CDC, a person who is addicted to prescription opioids is 40 times more likely to use heroin compared with a person who is not. Every addicted prescription opioid user who I have talked with started out as a recreational user. Since I only see people with addictions, the only recreational users of opioids who I see, could not tolerate opioids and moved on to something else.

The crux of Dr. Hart's argument seems to be that focus on neuroscience has led to malignant law enforcement efforts to eliminate drug use from marginalized citizens. He cites the differences in the legal penalties for crack cocaine as opposed to powdered cocaine a frequent illustration of discrimination against blacks as opposed to suburban whites. He seems to ignore that fact that drug and alcohol use takes a heavy toll and that toll occurs independent of race. The leap from neuroscience to politics and law enforcement is quite a leap. Is it possible for example that the police, the prosecutors and the politicians involved are more likely to discriminate against the marginalized citizens that Hart refers to? I would say it is highly likely and would offer several of the posts on this blog documenting active discrimination from politicians and insurance companies against addicts and the mentally ill. None of the people making those discriminatory policies, rationing resources or denying rational treatment care one bit about neuroscience. Most of them barely know that the brain is located in the head.

Let me conclude with what is know about addictions and why that knowledge is only peripherally related to politics. A significant portion of the population is at risk for addiction. Many of them know it because they notice that there are several generations of addicts and/or alcoholics in their family and in general - most people can see that trend without talking to professional. Exposure to drugs or alcohol is the other critical variable. Contrary to the suggestion of recreational use, people predisposed to addictions recognize early on that their pattern of use is distinct from that of their peers. They recognize at one point that their ability to control it is gone. They recognize it is taking a heavy toll on their physical health, mental health, finances, and relationships but they can't stop. They recognize neurobiological features like craving, tolerance, and withdrawal. More importantly for the purposes of Dr. Hart's argument - addiction is an equal opportunity disease. Racism has certainly suggested otherwise on a historical basis, but the opioid epidemic and its reach into rural America has illustrated that anyone can become a heroin addict. Exposure to the drug is the critical factor and not the few genes that determine skin color.

You can call that a disease if you want and most lay people and physicians would agree with you. My only qualification is that the definition of disease is very imprecise. People arguing that addiction is not a disease seem to not know that. Are there demonstrable changes due to addiction in animal models and humans? Of course there are and most modern addiction medicine text books exhaustively list them in each chapter on a specific addictive drug. It is much more specific to call an addiction what it is, cite the actual neurobiology and study it - just like modern approaches to any number of difficult biological problems in medicine.

That doesn't rule out psychosocial research on addiction. That research happens all of the time. The problem is the same problem that was previously noted in psychiatric research. We have 30 years of research proven psychosocial therapies in psychiatry. They have modest effect sizes, but the problem is that nobody will pay for them. There is a strong overlap with addiction since many of the therapies are similar. The real cause of discrimination is not at the level of the scientific community. The real cause of discrimination occurs at the levels of the bureaucrats running the healthcare system and a political system that is clearly set up to favor businesses and the wealthy.